1. Field of the Invention
This invention relates to a surgical needle assembly for performing hand-held surgical medical procedures such as obtaining subcutaneous tissue cell samples and, more particularly, to an improved cannula hub and cooperating stylet cap for quickly and surely determining the orientation of the stylet with respect to the cannula before commencement of the procedure.
2. Description of Related Art
Several medical procedures have been developed which make use of a hand-held surgical needle assembly comprising, among other elements, a cannula and a stylet. Such procedures include biopsy, angiography, and spinal and epidural procedures. The biopsy procedure is used to obtain subcutaneous biopsy tissue samples and cell samples for detailed analysis. Biopsy procedures range from surgical examination of the internal tissue and large-bore core biopsies, to a less intrusive procedure commonly known as fine-needle aspiration. In this procedure, a fine or thin biopsy needle, sometimes called a "skinny needle" is introduced by penetration into the patient's body, and its tip is brought into contact with the tissue to be sampled. Suction or negative pressure is applied to the outboard end of the needle thereby drawing fluid and cells of the tissue to be sampled into the needle for removal from the patient. Because the needles used in aspiration biopsy procedures are fine or narrow, this procedure is minimally intrusive and can most often be performed in the physician's office as outpatient surgery. Fine-needle aspiration biopsies have replaced a large number of the more intrusive surgical biopsies previously performed.
The needle used for the aspiration procedure typically comprises a cannula formed with a contoured distal end and a stylet formed with a matching contour at its distal end. The stylet is received snugly but freely slidably within the lumen of the cannula to provide rigidity and a solid end for the needle, as opposed to a hollow tip, for introduction of the needle into the patient's body. After the tip or distal end of the needle reaches the tissue to be sampled, the stylet is removed, whereupon negative pressure may be applied to the hub of the cannula.
A wide variety of contour shapes for the distal ends of the cannula and stylet have been developed and may be employed in conjunction with the invention. In most cases, it is imperative that the stylet have a certain angular or rotational orientation with respect to the cannula as the needle is introduced into the patient's body to minimize trauma. Several different means have previously been incorporated in a handle or hub of the cannula and a cap of the stylet to indicate and maintain proper angular orientation of the stylet with respect to the cannula. The cannula hub typically comprises a solid member for mounting the cannula which the physician may grasp when using the needle. The cannula hub has an aperture for telescopically receiving the stylet. The stylet cap traditionally comprises a hollow cap which is telescopically received on the cannula hub. The cap also supports the stylet.
An example of a cooperating stylet cap and cannula hub is disclosed in U.S. Pat. No. 3,175,554, issued Mar. 30, 1965, to R. A. Stewart. Stewart illustrates a radially extending lug on the stylet cap which cooperates with a notch on the cannula hub to obtain the desired orientation of the stylet with respect to the cannula. U.S. Pat. No. 4,655,226, issued Apr. 7, 1987, to P. F. Lee, discloses a longitudinally extending lug on the stylet cap which interacts with a notch on the cannula handle to maintain proper angular orientation. A similar device is disclosed in U.S. Pat. No. 4,846,804, issued Jul. 11, 1989 to R. E. Davis et al. U.S. Pat. No. 4,266,555, issued May 12, 1981 to K. Jamshidi discloses a flat surface on a cylindrical stylet cap and cylindrical bore of a cannula hub to maintain the angular orientation. A lug and L-shaped channel are employed on the stylet cap and cannula hub in U.S. Pat. No. 3,630,192, issued Dec. 28, 1971 to K. Jamshidi, U.S. Pat. No. 4,609,370, issued Sep. 2, 1986 to P. C. Morrison, and U.S. Pat. No. 3,628,524, issued Dec. 21, 1971 to K. Jamshidi.
These prior references disclose various needle constructions in which mechanical interlocking means are provided to establish the angular orientation between the stylet and cannula of a needle. None of the needles disclosed in the prior art identified hereinabove includes simple visual means for checking the angular orientation of the stylet with the respect to the cannula. In addition, the prior devices as disclosed fail to show simple means to verify the angular orientation of the stylet and the cannula by touch.